Police block a road near the house where Nancy Lanza was gunned down by her son Adam before he killed dozens at a school five miles away.

Photo: Don Emmert, AFP/Getty Images

Police block a road near the house where Nancy Lanza was gunned...

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This undated photo shows Adam Lanza posing for a group photo of the technology club which appeared in the Newtown High School yearbook. Authorities have identified Lanza as the gunman who killed his mother at their home and then opened fire Friday, Dec. 14, 2012, inside an elementary school in Newtown, Conn., killing 26 people, including 20 children, before killing himself. Richard Novia, a one-time adviser to the technology club, verified that the photo shows Lanza. (AP Photo)

Photo: Associated Press

This undated photo shows Adam Lanza posing for a group photo of the...

Newtown, Conn. -- The gunman who killed 27 people, including 20 children, targeted a school to which he had no current connection - forcing his way in and spraying classrooms with a weapon designed to kill across a battlefield, authorities said Saturday.

Law enforcement officials gave new details about Friday's rampage by Adam Lanza, which ended with his suicide. Their new narrative partially contradicted previous ones, and made a baffling act seem more so.

Lanza's mother, for instance, was not a teacher at Sandy Hook Elementary School. She apparently was unemployed. So it was still a mystery why her son - after dressing in black, killing his mother, and taking at least three guns from her collection - drove the five miles to the school, although investigators believe he may have been a student there years ago.

The part of the story that remained grimly, awfully unchanged was what Lanza did when he got there.

Authorities on Saturday released the names of those Lanza killed at the school, who ranged in age from 6 to 56. And the state's medical examiner - speaking in sanitized, clinical terms - described the results of something deeply obscene: a semiautomatic rifle fired inside an elementary classroom.

"I've been at this for a third of a century. And my sensibilities may not be the average man's. But this probably is the worst I have seen," said H. Wayne Carver II. Carver described the children's injuries, which he said ranged from two to 11 bullet wounds apiece.

He had performed seven of the autopsies himself. A reporter asked what the children had been wearing. "They're wearing cute kid stuff," Carver said. "I mean, they're first-graders."

On Saturday, the small New England town and the country played out what is now a familiar ritual: the dumbstruck aftermath of a young gunman's massacre. Word came that President Obama would arrive Sunday for an evening interfaith service, repeating a familiar role, as chief mourner.

People who had known Lanza described him as odd, nervous and withdrawn, and searched their memories for signs they had missed. Memorials went up. Politicians talked - a little more forcefully this time - about how someone needed to be brave enough to discuss guns and gun control.

And, in Newtown, they started funeral preparations. This time, the ritual was for lives so new that it seemed impossible to speak of them in the past tense.

"He was just in the wrong place at the wrong time," said Rabbi Shaul Praver of Adath Israel, who said that his congregation lost a first-grade boy. "His little body could not endure so many bullets like that."

On Saturday, law enforcement officials said that Lanza had entered the school by force sometime after 9:30 a.m. Friday. Sandy Hook's principal, Dawn Hochsprung, had recently installed a new security system in which the school doors were kept locked all day starting at 9:30. But Lanza had apparently shattered the glass in a window or door.

Lanza was carrying at least three guns from a collection maintained by his mother, who friends said enjoyed target shooting. Lanza had two pistols, a Glock and a Sig Sauer.

But he apparently chose a larger weapon, a .223-caliber Bushmaster rifle. This rifle fires one bullet for every pull of the trigger and sends a slug out at an unusually high speed. Authorities said Lanza fired dozens and dozens of times in a spree that lasted minutes.

"All the wounds that I know of at this point were caused by the long rifle," Carver, the medical examiner, said.

When police arrived, Lanza was dead. So were Hochsprung and five other adults. So were 18 children. Two more later died of their wounds at a local hospital.

Later, when investigators went to the home that Lanza shared with his mother, Nancy Lanza was found dead there - the first victim of the killings and the last discovered.

On Saturday, authorities said they had "very good evidence" regarding Adam Lanza's motives. But they didn't say what that evidence was.

Those who knew Lanza were left to puzzle.

"He was very, very quiet, reserved, shy, kept to himself," said Marsha Moskowitz, his middle school bus driver. "He'd say hello and goodbye, and that was about it."

Around the country, advocates for stronger gun-control laws said they hoped that the shock of this crime would start a debate that other mass shootings had not. Still, with so little known about Adam Lanza and the guns he used, it was difficult to say what sort of law, precisely, was needed to prevent another shooting like Friday's.

"If having dozens of people gunned down in an elementary school doesn't motivate Washington to do even the easy things they can do, it's not clear what will," said Mark Glaze, director of Mayors Against Illegal Guns, a group chaired by New York Mayor Michael Bloomberg, a political independent, that represents 750 mayors across the country.